The present invention relates to an optical element retaining member for retaining optical fibers, optical semiconductor elements which are used in optical connectors, optical modules and so on.
Conventionally substrates are used which are provided with a plurality of grooves as the retaining members for the optical fibers. For example, a retaining member 10 shown in FIG. 6, (a) and FIG. 6(b) is a plate-shaped body with a V-shaped groove 13 being formed for retaining the optical fiber. When bare fibers 21 each having the jacket of the optical fiber 20 peeled off are arranged side by side in the V-shaped grooves 13. Glass 16 is fixedly filled in the gap of both by covering the bare fibers with a cover body 15, each bare fiber 21 is firmly supported at three points and a plurality of optical fibers 20 can be retained in regular order with high accuracy. Furthermore, a groove 14 can be provided in order to insert a guide pin for positioning use into both the end portions of the groove 13 for retaining the optical fiber use (refer to Japanese Laid-Open Patent Application Tokkaisho 62-215208).
It can be used as an optical connector with the end face 10a of the retaining member 10 being brought into contact with each other or it can be used as an optical module with an optical waveguide path being connected with the end face 10a of the retaining member 10 or a receiving light emitting element being connected.
As a material quality of the retaining member 10 and the cover body 15 various types of ceramic or glass can be used. A groove 13 precisely worked is formed through a precise working operation on the retaining member 10. Since a step of forming the groove 13 by conducting the precise working operation upon the retaining member 10 requires much labor extremely, it is required to work with high accuracy the groove 13 by a step as simple as possible.
Recently, it is conducted to form a V-shaped groove by an etching operation by using a silicon substrate. As shown in FIG. 7(a), a heat oxide film is formed as masking 31 on the retaining member 10, made of a single crystal silicon plate-shaped body made to become a predetermined crystal bearing. As shown in FIG. 7(b), The resist 32 is patterned to remove the heat oxide film in a portion for forming the groove 13. Then, as shown in FIG. 7(c) the heat oxide film is etched using buffer fluorine to form an opening portion 33. As shown in FIG. 7(d), only a portion free from masking 31 is etched by conducting an anisotropy etching operation with the use of potassium hydroxide or the like. In addition, an etching operation is conducted along the V-shape along the crystal face of the silicon, so as to form the V-shaped groove 13. Therefore, as shown in FIG. 7(e), the V-shaped groove 13 of a determined depth can be formed into high precision by the managing of the etching conditions.
The receiving light emitting element 22 is directly mounted, as shown in FIG. 7 (f), on the retaining member 10 made of silicon and the optical module can be constructed by retaining the optical fiber 20 in the groove 13.
In the retaining member 10 made of silicon shown in FIG. 7, there is a problem in that long time is required to work the groove 13 for etching operation. A plurality of grooves 13 different in depth cannot be formed at the same time due to formation of the groove 13 by an etching operation. For example, as is shown in FIGS. 6(a) and 6(b), two types of grooves 13 for retaining the optical fiber and the grooves 14 for guide pin inserting use cannot be formed in the same time. Since the etching operation can be conducted further along the crystal face in the etching operation of the silicon, a working operation can be conducted only in the V shape, preventing an angular groove or a round groove from being formed. A reinforcing plate is inconveniently required, because the retaining member 10 made of silicon is lower in strength.
In the retaining member 10 of ceramic or glass, much labor is required in working the groove 13, as aforementioned above, although the strength is high.
The optical element retaining member of this invention is characterized in that a plurality of convex portions made of ceramic, glass, silicon or the like are integrally spliced with each other on a substrate made of ceramic, glass silicon or the like, and optical elements such as optical fibers, optical semiconductor elements or the like are retained in the concave portions among the convex portions.
In the invention, the intervals of these convex portions are made concave for retaining the optical elements by integrated bonding operation of the convex portions in the predetermined position on the substrate, instead of shaving the concave portions such as grooves from the substrate. Thus, the etching and precise working operations are not necessary to be conducted. The concave portion of high precision can be formed by a simple step.
The optical elements of the invention are referred to as the general optical elements such as ferrules or the like for retaining lens, filter, mirror, optical isolator, optical fiber, in addition to the optical fibers and optical semiconductor elements. The concave portion of the invention indicates not only a groove, but also a position of shape lower than the surrounding.
According to the invention, a mixture material between powder such as ceramic, glass, silicon or the like, and a binder composed of a solvent and an organic filling material is filled into a mold having a concave portion for convex portion use. Then, an optical fiber retaining member is produced from a step of bonding and integrating the mixtures material with the substrate face composed of ceramic, glass, silicon or the like.
Therefore, the mixture material of the convex portion material is filled into a mold including the concave portion, for convex portion use, prepared in advance and the mixture is bonded and integrated on the substrate, so as to transfer the shape of the mold as they are on the substrate. Thus, when the mold is made in advance with high precision, it is possible to mold with high precision the convex portion and the concave portion formed between them.
The integral bonding operation of the convex portion and the substrate includes steps of filling the mixture material into the mold including the concave portion, having releasing, burning operations after fixedly adhering it onto the substrate, or steps of filling the mixture material into the mold, fixing it and then, releasing it, adhering it on the substrate, burning it, or steps of filling the mixture into the mold, fixing it and then, releasing, burning it, bonding it on the substrate or thermally adhering it. It is possible to use a method of bonding between the general glass or the ceramic.